Carbon fibers have been known as a material having excellent dynamic characteristics such as high intensity and high elasticity. Carbon fiber reinforced plastic (hereinafter also referred to as CFRP) that uses the carbon fibers as a filer component and an epoxy resin, a polyester resin, or the like as a matrix component has been manufactured. Carbon fiber has a light weight as ¼ of the specific weight of iron, has an intensity of 10 times as high as that of iron, and is a material excellent in abrasion resistance, heat resistance, electrical conductivity and tensile resistance, and thus, carbon fibers have been widely used in various industrial fields typically including the aerospace industry.
Carbon fiber reinforced plastic is mainly manufactured by generating a prepreg obtained by permeating a resin being a matrix component into carbon fibers and firing this prepreg in an autoclave with pressurization. In this manufacturing step of carbon fiber reinforced plastic, many mill ends are generated other than products. For example, when a large-sized product such as a body of an airplane is manufactured, a large amount of such mill ends described above are generated. Therefore, disposal of such mill ends has been a problem in some cases. As described above, carbon fiber reinforced plastic is a material in which different characterized filler components and matrix components exist in mixture and separation of these components and recycle or reuse of them were technically highly difficult. In addition, it was not effective from the viewpoints of cost and energy efficiency. As a result, in the present circumstances, a large portion of mill ends generated in manufacture and unused prepreg have been disposed by landfill, incineration, and the like. Furthermore, carbon fiber reinforced plastic recovered after completion of functions as a product has been similarly disposed by landfill, and the like in the same manner.
The inventors of the present invention have already developed a technology that relates to a regeneration device and a regeneration method of carbon fibers in which only a matrix component is heated and removed from carbon fiber reinforced plastic by thermal decomposition and carbon fibers are selectively recovered without lowering dynamic characteristics (see Patent Literature 1 and Patent Literature 2). According to the technology, an elongated tunnel-shaped regeneration space is constructed with a fire resistant material in a continuous furnace. In this continuous furnace, a mesh belt conveyor is arranged. Carbon fiber reinforced plastic is continuously supplied to the regeneration space in use of such a belt conveyor and, at the same time, carbon fiber reinforced plastic is heated in a heating zone in the regeneration space, thereby gasifying only a matrix component such as a thermoplastic epoxy resin by thermal decomposition, which makes it possible to recover carbon fibers (recycled carbon fibers) in a long fibrous state. As a result, a large amount of carbon fiber reinforced plastic can be effectively thermally decomposed and recycled carbon fibers can be thus generated.
In addition, Patent Literature 3 discloses a technology of recovering carbon fibers in a state of removing 68 to 80% of plastic by treating carbon fiber reinforced plastic with overheated steam at 800° C. or higher. Patent Literature 3 discloses a recovery device provided with a heater part that produces overheated steam, an introduction part that introduces the produced steam, and a holding part that maintains carbon fiber reinforced plastic.